The present invention relates to a two-cycle engine, especially for a portable, manually-guided implement such as a power chain saw, a cut-off machine, or the like.
WO 99/18338 (EP 0 971 110 A1) discloses a two-cycle engine to which combustion air is supplied via an air channel. The air channel opens via a diaphragm valve into a transfer channel. To achieve low exhaust gas values, the ratio of the previously stored air to the fuel/air mixture supplied to the crankcase is 0.7 to 1.4. The diaphragm valve opens and closes due to different pressure levels in the air channel and crankcase. The air quantity supplied to the transfer channels is thus dependent upon the existing pressure conditions. Since these pressure conditions vary with respect to the speed, too much air is supplied via the transfer channels to such an internal combustion engine at low speeds. The fuel/air mixture supply to the combustion chamber therefore becomes lean, resulting in a poor operating characteristic in the low speed range.
It is therefore an object of the present invention to provide a two-cycle engine of the aforementioned general type according to which, at advantageous operating characteristics, good exhaust gas values are achieved in all speed ranges.